Method for the operation of a drivetrain

ABSTRACT

A method of operating of a drivetrain, having at least a drive motor and an automatic transmission with at least five shift elements, to improve a shift speed such that during a first upshift or a first downshift, at least one required shift element is prepared such that, when a synchronization point is reached, the successive upshift or the successive downshift can be immediately carried out. The method comprises the steps of requiring, at most, two of the at least five shift elements be disengaged and a remainder of the shift elements be disengaged for each gear for transferring one of torque and force; and one of increasing and decreasing a torque of the drive motor, relative to a torque of the drive motor derived from a driver&#39;s wish, during one of the first upshift or downshift and the successive upshift or downshift to assist with an overlapped implementation of the successive upshifts or the successive downshifts.

This application is a divisional application of U.S. Ser. No. 11/811,208filed on Jun. 7, 2007 and claims priority from German Application SerialNo. 10 2006 026 602.1 filed Jun. 7, 2006.

FIELD OF THE INVENTION

The invention concerns a method for the operation of a drivetrain of amotor vehicle, comprising at least an automatic transmission and a drivemotor.

BACKGROUND OF THE INVENTION

The main components of a motor vehicle drivetrain are a drive motor anda transmission. A transmission converts torques and speeds and sotransforms the traction force provided by the drive motor. The presentinvention concerns a method for the operation of a drivetrain whichcomprises at least a drive motor and an automatic transmission. In thecontext of the present invention the term “automatic transmission” isunderstood to mean any transmission that effects automatic gear changes,these also being known as variable-speed transmissions.

From DE 100 35 479 A1, a method is known for operating an automatictransmission, in which successive upshifts and downshifts can be carriedout with some overlap in order to improve the shift speed. For this,during each first upshift or downshift, a shift element needed for thesubsequent second upshift or downshift is prepared, while the firstupshift or downshift is in progress, in such a manner that when asynchronization point, namely a synchronous speed of the first upshiftor downshift in progress is reached, the subsequent second upshift ordownshift can be carried out immediately.

In this way, according to DE 100 35 479 A1, single shifts are overlappedwith one another, which means that each first upshift or downshiftcarried out and each subsequent second upshift or downshift is a singleshift between two directly successive gears.

The method known from DE 100 35 479 A1 can be used with an automatictransmission comprising five shift elements of which, for torque andforce transfer in any forward gear and in a reverse gear, in each case,two shift elements are engaged and three shift elements are disengaged.With such an automatic transmission six forward gears can be engaged. Inthe development of automatic transmissions, however, a trend isperceptible towards constantly increasing the number of gears, inparticular, forward gears of the automatic transmission. Thus atpresent, automatic transmissions with eight forward gears and onereverse gear are being developed, such automatic transmissions having atleast five shift elements such that, for torque or force transfer, atleast two of these at least five shift elements are disengaged in anyforward gear and in a reverse gear while the other shift elements areengaged. For such an automatic transmission, the method known from DE100 35 479 A1 is not suitable.

Starting from this, the present invention addresses the problem ofproviding a new type of method for the operation of a drivetraincomprising at least an automatic transmission and a drive motor.

SUMMARY OF THE INVENTION

According to a first embodiment of the invention, in an automatictransmission with at least five shift elements of which, for torque orforce transfer in any forward gear and in a reverse gear, in each case,at least two shift elements are disengaged and the other shift elementsare engaged, two respective consecutive upshifts or two respectiveconsecutive downshifts can be carried out with overlap in such mannerthat:

-   a) when carrying out a first upshift or downshift, in accordance    with a first alternative a first shift element is disengaged or, in    accordance with a second alternative, it is engaged and, in    accordance with the first alternative, a second shift element is    engaged or in accordance with the second alternative it is    disengaged;-   b) while the first upshift or downshift is being carried out with a    view to a subsequent second upshift or downshift, a second shift    element is prepared for disengaging in accordance with the first    alternative or for engaging, in accordance with the second    alternative, and a third shift element is prepared for engaging, in    accordance with the first alternative or for disengaging in    accordance with the second alternative, the second shift element,    selected from a minimum number or a maximum number of shift    elements, is actuated on transition from the first upshift or    downshift to the second upshift or downshift;-   c) while the first upshift or downshift is being carried out and    while the second upshift or downshift is being carried out, at least    one fourth shift element is kept engaged or nearly engaged.

According to a second embodiment of the invention, in an automatictransmission with at least five shift elements of which, for torque orforce transfer in any forward gear and in a reverse gear, in each case,at least two shift elements are disengaged and the other shift elementsare engaged, while a first upshift or downshift is being carried out andwith a view to a subsequent second upshift or downshift, a shiftelement, that is to be engaged during the second upshift or downshift,is prepared for engaging at a time before the synchronization point ofthe first upshift or downshift has been reached, by a time interval thatcan be applied in a time-controlled or in an event-controlled manner.

According to a third embodiment of the invention, in an automatictransmission with at least five shift elements, of which, for torque orforce transfer in any forward gear and in a reverse gear, in each caseat most two shift elements are disengaged and the other shift elementare engaged, while a first upshift or downshift and/or while a secondsubsequent upshift or downshift is being carried out, a torque of thedrive motor is increased and/or decreased compared with a drive motortorque deduced from a driver's wish, in order to assist the overlappedimplementation of successive upshifts or downshifts.

The above three embodiments, according to the invention, can be usedeither alone or in a combination of two embodiments or in a combinationof all three embodiments for the operation of a drivetrain.

BRIEF DESCRIPTION OF THE INVENTION

Preferred further developments of the invention emerge from thesubordinate claims and from the description given below. Exampleembodiments of the invention are explained in greater detail withreference to the drawing, without being limited thereto.

FIG. 1 is a drivetrain layout of a motor vehicle;

FIG. 2 is a transmission layout of an automatic transmission of thedrivetrain with five shift elements;

FIG. 3 is a shift element matrix for the shift elements of thetransmission layout in FIG. 2, to indicate which shift elements areengaged in which gear;

FIG. 4 is a first diagram to aid in understanding the method, accordingto the invention, for operating a drivetrain of a motor vehicle, whichcomprises an automatic transmission according to FIGS. 2 and 3;

FIG. 5 is a s second diagram to aid in understanding the method,according to the invention, for operating a drivetrain of a motorvehicle, which comprises an automatic transmission according to FIGS. 2and 3; and

FIG. 6 is a third diagram to aid in understanding the method, accordingto the invention, for operating a drivetrain of a motor vehicle, whichcomprises an automatic transmission according to FIGS. 2 and 3.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a very schematic representation of a drivetrain of a motorvehicle, the drivetrain comprising a drive motor 1, an automatictransmission 2 and a drive wheel 3 of the motor vehicle. The automatictransmission 2 transfers the traction force produced by the drive motor1 to the wheels 3 of the motor vehicle.

When the drivetrain according to FIG. 1 is operated in traction mode, apower flows in the direction of arrow 4 from the drive motor 1 towardthe wheels 3 of the motor vehicle. In contrast, if the drivetrain isoperated in thrust mode, for example, when braking or coasting, thepower flows in the direction of arrow 5, from the wheels 3 toward thedrive motor 1.

The invention concerns a method for the operation of a drivetraincomprising a drive motor 1 and an automatic transmission 2, theautomatic transmission 2 having at least five shift elements such that,for torque or force transfer, at most two shift elements are disengagedin any forward gear and in a reverse gear while the other shift elementsare engaged. An example of such an automatic transmission is shown inFIGS. 2 and 3. Although in what follows the invention is described inmore detail with reference to the example, it is not limited in itsapplication to this example of an automatic transmission.

FIG. 2 shows a transmission layout 6 of a variable-speed automatictransmission 2 comprising four transmission gearsets 7, 8, 9 and 10 forthe conversion of a transmission input torque, applied to a transmissioninput 11, into a transmission output torque of a transmission output 12.According to FIG. 2, the transmission gearsets 7, 8, 9 and 10 of theautomatic transmission 2 are planetary transmission gearsets. Accordingto the transmission layout 6 of FIG. 2, besides the four transmissiongearsets 7-10 the automatic transmission also has five shift elements13, 14, 15, 16 and 17. Shift element 13 is denoted shift element A;shift element 14 as shift element B; shift element 15 as shift elementC; shift element 16 as shift element D, and shift element 17 as shiftelement E. Shift elements A and B are each brakes, while each of shiftelements C, D and E is a clutch.

For the automatic transmission represented schematically in FIG. 2,comprising the five shift elements 13-17, application of the shiftmatrix 18 shown in FIG. 4 enables eight forward gears and one reversegear to be engaged, the eight forward gears “1“-”8” and the reverse gear“R” being entered in the left-hand column of the shift matrix 18 and theshift elements A-E along the top line of the matrix 18. Shift elementsmarked with a spot in the shift element matrix 18 are engaged when thecorresponding gear is engaged. According to the matrix, in each forwardgear and in the reverse gear, respectively three of the five shiftelements are engaged and two shift elements are disengaged in each case.Thus for example, for forward gear “1” the shift elements A, B and C areengaged and the shift elements D and E are disengaged. For the reversegear “R” shift elements A, B and D are engaged and shift elements C andE are disengaged. Accordingly, in each gear at most two respective shiftelements are disengaged.

To improve the shifting speed successive upshifts or successivedownshifts, they are carried out with some overlap, such that during afirst upshift or downshift at least one shift element needed for thesubsequent second upshift or downshift is prepared while the firstupshift or downshift is in progress, and this in such manner that assoon as a synchronization point of the first upshift or downshift inprogress is reached, the next second upshift or downshift can be carriedout immediately.

The Table below shows in its left-hand column examples of the downshiftsand upshifts that can be carried out with overlap by the automatictransmission 2 shown in FIGS. 2, 3, such that when, in the left-handcolumn, a downshift or upshift is entered in brackets after anotherdownshift or upshift, the downshift or upshift not in brackets is thefirst downshift or upshift and the downshift or upshift in brackets isthe second downshift or upshift, for which at least one shift element isprepared while the first downshift or upshift is in progress.

In the Table shift elements which are engaged and thus engaged during afirst upshift or downshift to be carried out are denoted “e”. Shiftelements which, in contrast, are disengaged and thus disengaged during afirst upshift or downshift are denoted “d” in the above table. Shiftelements which, during a first upshift or downshift, are prepared forclosing and thus engagement or for disengaging and thus disengagementwith a view to a subsequent, second upshift or downshift, arerespectively denoted “pe” or “pd” in the above table.

When shift elements are marked “e/pd” or “d/pe” in the Table, this meansthat the shift elements in question are involved in both the first andin the subsequent second upshift or downshift, so that on transitionfrom the first upshift or downshift, there is a minimum or a maximumnumber of shift elements available for implementation. Shift elementsmarked “x” are and remain engaged during an upshift or downshift. Incontrast, shift elements marked “-” are and remain disengaged during anupshift or downshift.

SHIFT ELEMENTS A B C D E DOWNSHIFT d/pe 8-7 (7-6) pd — e x e/pd 7-6(6-5) d pe — x d/pe 6-5 (6-4) — e pd x e 5-4 (4-3) — x d/pe pd — 4-3(3-2) pe x e/pd d pd 3-2 (2-1) e x d/pe — x 6-4 (4-3) — e d/pe pd x 8-6(6-4) d pe e/pd x e/pd 5-3 (3-1) pe x x d UPSHIFT 1-2 (2-3) pd x d/pe —e 2-3 (3-4) d x e/pd pe x 3-4 (4-5) — x d/pe e pd 4-5 (5-6) — pd e xd/pe 5-6 (6-7) pe d x x e/pd 6-7 (7-8) e — pd x d/pe 3-5 (5-6) — pd x ed/pe 4-6 (6-8) pe d e/pd x x

In using the above Table for the automatic transmission of FIGS. 2 and3, depending on the gear change that is to be carried out from a currentgear to a desired gear, either multiple shifts or single shifts arecarried out as both the first upshifts and the first downshifts. While amultiple shift is in progress as the first upshift or downshift, asingle or multiple shift is prepared for as the second, subsequentupshift or downshift. Upshifts or downshifts carried out as multipleshifts are double shifts.

According to a first embodiment of the present invention, in accordancewith a first alternative when a first upshift or downshift is carriedout, a first shift element is disengaged and thus disengaged and asecond shift element is engaged and thus engaged. While this firstupshift or downshift is being carried out, with a view to the subsequentsecond upshift or downshift the second shift element is prepared fordisengaging and thus disengagement. While the first upshift or downshiftis in progress, a third shift element is prepared for closing and thusengagement. While the first and also the second upshifts or downshiftsare in progress, at least a fourth shift element is kept engaged ornearly so.

On transition from the first upshift or downshift to the subsequentsecond upshift or downshift, the second shift element, which is activeboth in the first and in the subsequent second upshift or downshift, isactuated through selection of a minimal number of shift elements.

This first alternative of the first embodiment of the present inventionwill be described below with reference to FIG. 4, considering theexample of two successive downshifts carried out as overlapping singleshifts. According to the above table, these could be the downshifts 8-7(7-6), for example.

FIG. 4 shows the time variations of various signals: a signal variation19 represents a driver's-wish-dependent desired gear; a signal variation20 represents a target gear determined on the basis of the desired gear;a signal variation 21 represents a gear currently engaged; a signalvariation 22 represents a torque of the drive motor 1 of the drivetrain,and a signal variation 23 represents a speed of the drive motor 1. Thesignal variations 24, 25, 26, 27 and 28 represent the actuation orbehavior, in time, of four shift elements involved in the overlappingimplementation of two successive downshifts; signal variation 24representing the time behavior of a first shift element to be closed andthus disengaged during the first downshift; signal variation 27representing the time behavior of the second shift element to be openedand thus disengaged during the first downshift; signal variation 26representing the time behavior of the second shift element to beprepared for opening and thus disengagement during the first downshiftwith a view to the subsequent second downshift, and signal variation 25representing the time behavior of the third shift element to be preparedfor closing and thus engagement during the implementation of the firstdownshift with a view to the subsequent second downshift. Signalvariation 28 represents the time behavior of the fourth shift element,which is kept engaged or nearly engaged while the first downshift andwhile the second downshift are in progress.

Thus, the signal variations 26 and 27 each concern the second shiftelement, which is active during both the first downshift and thesubsequent second downshift; in the signal variations 26 and 27 thesolid line represents an active operating sequence of the second shiftelement and the broken line represents a passive background calculationfor the second shift element.

At time A, there is a change of the desired gear (see signal variation19) and, derived from this, a change of the target gear (see signalvariation 20) by way of a desired downshift through one gear (x−1), thisthen triggering the overlapped implementation or preparation ofsuccessive downshifts, namely in such a manner that at time A, on onehand, the first shift element that is to be opened and thus disengagedwhile the first downshift is carried out (see signal variation 24)begins its shift phase and, on the other hand, the second shift elementthat is to be closed and thus engaged while the first downshift iscarried out (see signal variation 27) undergoes rapid filling, whichtakes place between times A and B.

The second shift element, which is to be prepared with a view to thesubsequent second downshift by way of a background calculation while thefirst downshift is in progress (see signal variation 26), and the thirdshift element (see signal variation 25) are set to a defined conditionat time A. The fourth shift element (see signal variation 28) remainsengaged.

On completion of the rapid filling of the second shift element that isto be closed and, therefore, engaged in the first downshift (see signalvariation 27), the second shift element changes from the rapid fillingphase to a filling equalization phase, this filling equalization phaseextending between times B and D.

The rapid filling phase between times A and B and the fillingequalization phase between times B and D together define the entirefilling phase of the second shift element that is to be engaged duringthe first downshift. At time D, the second shift element to be closedand, therefore, engaged during the first downshift (see signal variation27), changes from the filling phase to the shift phase.

While the first downshift is being carried out, during which the firstshift element, in accordance with signal variation 24, is opened andthus disengaged and the second shift element, in accordance with signalvariation 27, is closed and thus engaged, shift elements are preparedfor a possible subsequent second downshift. Thus at time C, thepreparation of the third shift element (see signal variation 25), thatwill be closed and thus engaged in a possible subsequent seconddownshift, takes place by rapid filling, which lasts between times C andE. On completion of the rapid filling of the third shift element at timeE, begins a filling equalization phase which, as shown in FIG. 4, lastsuntil time G.

Likewise, while the first downshift is in progress, with a view to asubsequent second downshift, the second shift element, which was alreadyinvolved in the first downshift, is prepared for opening ordisengagement (see signal variation 26) by way of a passive backgroundcalculation. At time F, a transition phase of the second shift elementprepared for disengagement with a view to the subsequent seconddownshift is started and, at time H, which corresponds to asynchronization point of the first downshift, a change from the firstdownshift to the subsequent second downshift takes place. The fourthshift element is kept engaged (see signal variation 28).

At time H, for the second shift element, which is closed and thusengaged in the first downshift and opened and thus disengaged in thesubsequent second downshift, in relation to the first downshift, thereoccurs a transition from an active sequence to a passive backgroundcalculation and, in relation to the subsequent second downshift, atransition from a passive background calculation to an active sequence.Upon reaching time H or, at the latest, up reaching time I, the shiftelements prepared during the first downshift are accordingly the activeshift elements of the subsequent second downshift. The fourth shiftelement (see signal variation 28) is also kept engaged during the seconddownshift.

By analogy with the first downshift, during the subsequent seconddownshift, shift elements undergo preparation for a possible subsequentthird downshift (see signal variations 29 and 30).

All the downshifts listed in the above Table can be carried out inaccordance with the above procedure so that, for example, for thedownshifts 8-6 (6-4) two fourth shift elements are kept engaged duringthe first and during the subsequent second downshift.

According to a second embodiment of the present invention, duringimplementation of the first downshift, with a view to the subsequentsecond downshift, the third shift element that is to be engaged duringthe second downshift (see signal variation 25), is prepared for engagingby rapid filling at time C, which occurs before the synchronizationpoint of the first downshift, in progress, has been reached at time H bya first time interval T₁, applicable in a time-controlled orevent-controlled way. The first time interval T₁, applicable by time orevent control, for example, can be determined by way of a time reserveor a speed difference relative to the synchronization point H of thefirst downshift.

If time C, which as shown in FIG. 4, is determined from thesynchronization point H and the applicable time interval T₁, occurslater than the end of the rapid filling phase of the second shiftelement to be engaged, i.e., later than time B, then the preparation ofthe third shift element, which is to be engaged during the seconddownshift (see signal variation 25), is started immediately. On theother hand, determined from the synchronization point H of the firstdownshift in progress and from the applied first time interval T₁, iftime C occurs earlier than the end (time B) of the rapid filling phaseof the second shift element to be engaged during the first downshift,the preparation of the third shift element id delayed until the rapidfilling phase of the second shift element to be engaged during the firstdownshift has been completed.

As already mentioned, the third shift element, which is prepared forengaging, with a view to the second downshift, while the first downshiftis taking place (see signal variation 25), is changed at time G from thepreparation phase to the shift phase, this time G, occurring before thesynchronization point H of the first downshift has been reached by asecond time interval T₂, which can be determined as a function of timeor events.

As shown in FIG. 4, if this time G, determined from the synchronizationpoint H of the first downshift and the applicable second time intervalT₂, occurs later than the end of the rapid filling phase (time E) of thethird shift element that is to be engaged during the second downshift,the third shift element to be engaged during the second downshift, ischanged directly from the preparation phase to the shift phase.

On the other hand, if the time G, determined from the synchronizationpoint H of the first downshift in progress and the applicable secondtime interval T₂, occurs earlier than the end of the rapid filling phase(time E) of the third shift element due to be engaged during the seconddownshift, then the change of the third shift element from itspreparation phase to its shift phase is delayed until the rapid fillingphase of the third shift element has been completed.

As already explained above, the third shift element prepared by way of abackground calculation during the implementation of the first downshiftfor opening and thus disengagement with a view to the subsequent seconddownshift is changed at time F from its preparation phase to its shiftphase, this time F occurring before the synchronization point H of thefirst downshift has been reached by a third time interval T₃ applied ina time-controlled or event-controlled way. In the example embodimentshown, at time F, it is decided whether the second downshift, preparedfor during the first downshift, will actually be carried out. Namely, aprepared next downshift is only actually carried out if the driver sowishes. From FIG. 4, it can be seen that at time F, in accordance withthe signal variation 19, which represents the driver's wishes, a furtherdownshift (x−2) is called for in order to reach the desired gear so, inthe example of FIG. 4, the second downshift is then also actuallycarried out.

As already explained above, during the second downshift, correspondingshift elements are prepared in accordance with signal variations 29 and30 for a third subsequent downshift, such that in FIG. 4, with a view tothe third downshift to be prepared for during the second downshift, thecorresponding applicable first time interval T′₁, second time intervalT′₂ and third time interval T′₃ relate to a synchronization point H′ ofthe second downshift.

From FIG. 4, it can be seen that at a time defined by thesynchronization point H′ of the second downshift and the applicablethird time interval T′₃, on the basis of the signal variation 19 thatrepresents the driver's wishes, no further downshift is required toreach the desired gear, so the third downshift prepared for while thesecond downshift is taking place, is not carried out, but is insteaddiscontinued. As can be seen from FIG. 4, in accordance with the signalvariation 21, the current gear is set to a new value by recognition ofthe synchronization point H or H′ of a shift carried out while, inaccordance with the signal variation 20, the target gear changes to thenext gear or remains unchanged, depending on the desired gear, accordingto the signal variation 19.

According to a third embodiment of the present invention, in the exampleembodiment shown in FIG. 4, during implementation of the first downshiftand during that of the second downshift, torque from the drive motor isincreased and/or reduced, compared with a drive motor torque derivedfrom the driver's wish, to support the overlapped implementation of thesuccessive downshifts. Thus the signal variation 22, represented in FIG.4 as a solid line, corresponds to drive motor torque derived from adriver's wish.

According to a first variation, indicated in FIG. 4 as a dot-dash line,during the implementation of both the first and the second downshifts,the drive motor torque is increased, relative to the drive motor torquederived from the driver's wish. In contrast, according to a secondvariation, indicated in FIG. 4 as a dotted line, at the end of thesecond downshift, the drive motor torque is reduced relative to thedrive motor torque derived from the driver's wish. Below, bothvariations will be explained in more detail.

The increase of the drive motor torque, indicated in FIG. 4 as adot-dash line, relative to the drive motor torque derived from thedriver's wish, takes place when the drivetrain is operated either inthrust mode or in part-load traction mode. During every downshiftcarried out in thrust or part-load traction operation, the drive motortorque is increased, relative to the torque derived from the driver'swish, and during each downshift carried out, it is checked whether aprepared subsequent downshift corresponds to the driver's wish. This isdone at a time that depends, on one hand, on the synchronization point Hand, on the other hand, on the applicable third time interval T₃, i.e.,in the example embodiment of FIG. 4 at time F.

When, at this time, on the basis of the driver's wish, a subsequentdownshift is required, the amount of torque during the first downshiftis changed to the amount of torque during the second downshift and, itcan be seen in the example embodiment illustrated, that the amount oftorque during the second downshift is larger than during the firstdownshift. In contrast, the amount of torque of the second downshift issmaller than that of the first downshift. Likewise, the two torques canbe of equal size. Preferably, between the two torque increases there isa ramp-like transition.

In contrast, at the above time, defined by the synchronization point Hand the applicable third time interval T₃, and depending on the driver'swish, if no subsequent downshift is required, the prepared follow-updownshift is discontinued and the increase of drive motor torque isterminated to complete the shift. This is shown in FIG. 4 for the thirddownshift, prepared during the second downshift.

During the implementation and preparation of successive downshifts, whenthe drivetrain is operating in traction mode, during each downshiftcarried out, at a time set by way of a time- or event-control, namely atthe time that depends on the synchronization point H and the applicablethird time interval T₃, it is checked whether a prepared next shiftcorresponds to a driver's wish. As shown in FIG. 4 for the thirddownshift prepared for during the second downshift, if this is not thecase, the prepared follow-up downshift is discontinued and in order tocomplete the shift in traction operation, the drive motor torquereduction, represented in the signal variation 22 of FIG. 4 as a dottedline, relative to the torque derived from the driver's wish, is carriedout.

In contrast, at this time, when a subsequent downshift is desired, as isthe case in FIG. 4 for the second downshift prepared for during thefirst downshift, the reduction of drive motor torque is discontinued.Accordingly, torque reduction during downshifts only takes place when ashifting process is to be terminated, i.e., when no subsequent shift isrequired.

Furthermore, the above reduction of torque only takes place duringtraction operation, and then both under full load and under part load.On the other hand, during thrust operation, this torque reduction doesnot take place during downshifts.

In the example embodiment of FIG. 4, two successive downshifts can becarried out and prepared for by the actuation of four shift elements,such that as shown in FIG. 4, to carry out the first downshift, a firstshift element (see signal variation 24) is opened and thus disengagedand a second shift element (see signal variation 27) is closed and thusengaged.

While the first downshift is being carried out, with a view to thesubsequent second downshift, the second shift element (see signalvariation 26) is preparing for opening and thus disengagement and athird shift element (see signal variation 25) is prepared for closingand thus engagement. A fourth shift element (see signal variation 28) iskept engaged during the first and second downshifts. On transition fromthe first to the subsequent second downshift, the second shift elementis selected from a minimum number of shift elements between the signalvariations 26 and 27.

FIG. 6 shows a procedure, according to the invention, for carrying outand preparing successive upshifts as overlapped single shifts. Inrelation to the control of the four shift elements, in accordance withthe first and second embodiments of the present invention, there are nodifferences from the procedure of FIG. 4, so that to avoid unnecessaryrepetitions, the same indices will be used for the example in FIG. 6.

To carry out successive upshifts in accordance with FIG. 6, comparedwith carrying out successive downshifts as in FIG. 4, there is only onedifference relating to the third embodiment of the present invention,which concerns increasing or reducing the drive motor torque comparedwith a drive motor torque derived from a driver's wish. Thus accordingto FIG. 6, for successive upshifts during thrust operation of thedrivetrain, the torque is elevated for both upshifts in accordance withthe dot-dash line of signal variation 22 while, in contrast, duringtraction operation of the drivetrain, the torque is reduced for bothupshifts as shown by the dotted line of signal variation 22.

A second alternative of the first embodiment of the invention forcarrying out successive downshifts or successive upshifts as overlappedshifts is described below with reference to FIG. 5, considering theexample of successive downshifts, and again for the example embodimentof FIG. 5, the same indices are used as for that of FIG. 4.

Thus, according to the second alternative of the first embodiment of thepresent invention represented in FIG. 5, two successive downshifts canbe carried out by actuating four shift elements in such a manner that tocarry out the first downshift, a first shift element (see signalvariation 27) is closed and thus engaged and a second shift element (seesignal variation 24) is opened and thus disengaged.

While the first downshift is being carried out, with a view to asubsequent second downshift, the second shift element (see signalvariation 25) is prepared for closing and thus engagement by way of abackground calculation and a third shift element (see signal variation26) is prepared for opening and, therefore, disengagement. At least onefourth shift element (see signal variation 28) is kept engaged or nearlyengaged while the first downshift and the second downshift are beingcarried out.

Accordingly, in the example embodiment of FIG. 5 the second shiftelement has a dual function and is engaged during both the first and thesecond downshifts and in accordance with this second alternative of thefirst embodiment of the invention, the second shift element, selectedfrom a maximum number of shift elements, is activated when changing fromthe first downshift to the second downshift.

At time A in FIG. 5, there occurs a change of the desired gear (seesignal variation 19) and, derived from this, a change of the target gear(see signal variation 20) by way of a desired downshift by one gear(x−1), which triggers the overlapping implementation or preparation ofsuccessive downshifts, namely in such a manner that at time A, on onehand, the first shift element (signal variation 27) that is to be closedand thus engaged when the first downshift is carried out is subjected torapid filling, this rapid filling taking place between times A and Band, on the other hand, the second shift element (signal variation 24)that is to be opened and thus disengaged when the first downshift iscarried out, begins its shift phase.

The second shift element (signal variation 25), which is to be preparedby way of a background calculation for the subsequent second downshiftwhile the first downshift is being carried out and the third shiftelement (signal variation 26), are set to a defined condition at time A.The fourth shift element (signal variation 28) is kept engaged.

On completion of the rapid filling of the first shift element (signalvariation 27) to be closed and engaged for the first downshift, thefirst shift element passes from the rapid filling phase to a fillingequalization phase; this filling equalization phase lasting betweentimes B and D. Taken together, the rapid filling and fillingequalization phases define the entire filling phase of the first shiftelement to be engaged during the first downshift.

At time D, the first shift element (signal variation 27), which is to beclosed and thus engaged during the first downshift, is changed from thefilling phase to the shift phase.

During the implementation of the first downshift, in which the secondshift element (signal variation 24) is opened and thus disengaged andthe first shift element (signal variation 27) is closed and thusengaged, shift elements are prepared for the possibility that asubsequent second downshift has to be carried out. Thus at time C, thepreparation of the second shift element (signal variation 25) that willbe closed and thus engaged in the event of a subsequent seconddownshift, by way of a background calculation, takes place by rapidfilling, which lasts between times C and E. On completion of the rapidfilling at time E, the shift element changes to a filling equalizationphase which, as shown in FIG. 4, lasts until time G.

While the first downshift is being carried out, in case there is to be asubsequent second downshift, the third shift element (signal variation26) is also prepared for opening or disengagement. At time F, atransition phase of the third shift element, prepared for the subsequentsecond downshift, is started. The fourth shift element (signal variation28) is kept engaged.

Between times G and H, for the second shift element which is opened andthus disengaged in the first downshift and closed and, therefore,engaged in the subsequent second downshift, in relation to the firstdownshift, a transition from an active sequence to a passive backgroundcalculation and, in relation to the subsequent second downshift, atransition from a passive background calculation to an active sequence.Accordingly, on reaching time H, the shift elements prepared during thefirst downshift become the active shift elements of the subsequentsecond downshift. The fourth shift element (signal variation 28) is keptengaged.

By analogy with the first downshift, during the subsequent seconddownshift, shift elements are prepared for the eventuality of a thirdsubsequent downshift (see signal variations 29 and 30).

In relation to the second embodiment of the present invention, i.e., inrelation to the applicable time intervals T₁, T₂ and T₃ on whose basis,on one hand, the preparation of the shift element to be engaged duringthe second downshift and the transition of the shift elements to beengaged or disengaged during the second downshift from the preparationphase to the shift phase take place, the example embodiment of FIG. 5corresponds to the example embodiment of FIG. 4, so reference should bemade to the description given earlier in this connection.

Furthermore, in relation to the third embodiment of the presentinvention, the example embodiment of FIG. 5 corresponds to the exampleembodiment of FIG. 4, i.e., in relation to the details concerning thedrive motor torque increase or torque reduction while carrying outoverlapping downshifts. Concerning these details too, reference can bemade to the earlier descriptions.

Finally, let it also be said that of course successive upshifts can becarried out as overlapping single shifts by analogy with the exampleembodiment of FIG. 5, in accordance with the second alternative of thefirst embodiment of the invention.

The method according to the invention can be used with any automatictransmissions that have at least five shift elements, such that fortorque or force transfer, at most two of these at least five shiftelements are disengaged in any forward gear and in a reverse gear, whilethe other shift elements are engaged.

Reference numerals 1 drive motor 2 automatic transmission 3 wheel 4arrow 5 arrow 6 transmission layout 7 transmission gearset 8transmission gearset 9 transmission gearset 10 transmission gearset 11transmission input 12 transmission output 13 shift element A 14 shiftelement B 15 shift element C 16 shift element D 17 shift element E 18shift element matrix 19 signal variation 20 signal variation 21 signalvariation 22 signal variation 23 signal variation 24 signal variation 25signal variation 26 signal variation 27 signal variation 28 signalvariation 29 signal variation

1. A method of operation of a drivetrain of a motor vehicle comprisingat least an automatic transmission having an input shaft, an outputshaft and four planetary gear sets and a drive motor, such thatsuccessive upshifts or successive downshifts can be carried out withoverlap in such manner that during a first upshift or a downshift atleast one shift element required for a subsequent, second upshift ordownshift is prepared during the first upshift or downshift in progressin such a manner that when a synchronization point of the first upshiftor downshift in progress is reached, the subsequent second upshift ordownshift can be carried out immediately, the method comprising thesteps of: in an automatic transmission with at least five shiftelements, of which, for torque or force transfer, disengaging at mosttwo shift elements in any forward gear and in a reverse gear while theother shift elements being engaged, during the implementation of atleast one of a first upshift, a first downshift, a second, subsequentupshift a second, subsequent downshift, one of increasing and decreasinga torque of the drive motor, relative to a drive motor torque derivedfrom a driver's wish, in order to support the overlapped implementationof successive upshifts or downshifts.
 2. The method according to claim1, wherein to carry out successive downshifts during traction operationof the drivetrain, during each downshift carried out it is checked, at atime applicable by virtue of time or event control, whether a follow-upshift that has been prepared for corresponds to a driver's wish, and ifat the said time, on the basis of the driver's wish no follow-up shiftis desired, the prepared follow-up shift is discontinued and to end theshift a drive motor torque is reduced relative to the drive motor torquederived from the driver's wish, but if at the said time, on the basis ofthe driver's wish a follow-up shift is desired, the prepared follow-upshift is carried out and the drive motor torque is not reduced.
 3. Themethod according to claim 1, wherein to carry out successive downshiftswhen the drivetrain is in thrust operation or part-load tractionoperation, during each downshift carried out the torque of the drivemotor is increased relative to the drive motor torque derived from thedriver's wish, and during each downshift carried out it is checked, at atime applicable by virtue of time or event control, whether a follow-upshift that has been prepared for corresponds to a driver's wish, and ifat the said time, on the basis of the driver's wish a follow-up shift isdesired, a transition, in particular ramp-like, is effected between thetorque elevations of the successive downshifts, but if at the said time,on the basis of the driver's wish a follow-up shift is not desired, theprepared follow-up shift is discontinued and to end the shift the drivemotor torque elevation is ended.
 4. The method according to claim 1,wherein to carry out successive upshifts during traction operation ofthe drivetrain, during each upshift carried out the torque of the drivemotor is reduced relative to the torque derived from the driver's wish,and to carry out successive upshifts during thrust operation of thedrivetrain, during each upshift carried out the drive motor torque isincreased relative to the torque derived from the driver's wish.
 5. Amethod of operating of a drivetrain of a motor vehicle having at least adrive motor and an automatic transmission with at least five shiftelements, the method improving a shift speed of at least one of asuccessive upshift and a successive downshift, such that during a firstupshift or a first downshift, at least one shift element, required forthe respective successive upshift or the successive downshift, isprepared such that when a synchronization point of the first upshift orthe first downshift in progress is reached, the successive upshift orthe successive downshift can be immediately carried out, the methodcomprising the steps of: requiring, at most, two of the at least fiveshift elements be disengaged and a remainder of the at least five shiftelements be engaged, in each of a plurality of forward and reverse gearsfor transferring one of torque and force; and one of increasing anddecreasing a torque of the drive motor, relative to a torque of thedrive motor derived from a driver's wish, during at least one of thefirst upshift or the first downshift and the successive upshift or thesuccessive downshift to assist in overlapped implementation of thesuccessive upshifts or the successive downshifts.
 6. The methodaccording to claim 5, further comprising the step of checking, duringeach downshift carried out and at a time, applicable in atime-controlled manner or an event-controlled manner, whether a preparedfollow-up shift, corresponds with a driver's wish to carry out furthersuccessive downshifts during traction operation of the drivetrain, if nofollow-up shift is desired, the prepared follow-up shift is discontinuedand the torque of the drive motor torque is reduced relative to thetorque of the drive motor derived from the driver's wish, but if afollow-up shift is desired, on the basis of the driver's wish, theprepared follow-up shift is carried out and the torque of the drivemotor is not reduced.
 7. The method according to claim 5, furthercomprising the step of increasing the torque of the drive motor relativeto torque of the drive motor, derived from the driver's wish, duringeach downshift carried out and also checking, during each downshiftcarried out and at the time applicable in a time-controlled manner or anevent-controlled manner, whether a prepared follow-up shift correspondsto the driver's wish, to carry out a follow-up downshifts when thedrivetrain is in a thrust operation or a part-load traction operation,if the follow-up downshift is desired, a ramp-like transition, iseffected between torque levels of the follow-up downshifts, but if thefollow-up shift is not desired, the prepared follow-up shift isdiscontinued and the torque of the drive motor is discontinued toprevent the follow-up downshift.
 8. The method according to claim 6,further comprising the step of increasing the torque of the drive motorrelative to torque of the drive motor, derived from the driver's wish,during each downshift carried out and also checking, during eachdownshift carried out and at the time applicable in a time-controlledmanner or an event-controlled manner, whether a prepared follow-up shiftcorresponds to the driver's wish, to carry out a follow-up downshiftswhen the drivetrain is in a thrust operation or a part-load tractionoperation, if the follow-up downshift is desired, a ramp-liketransition, is effected between torque levels of the follow-updownshifts, but if the follow-up shift is not desired, the preparedfollow-up shift is discontinued and the torque of the drive motor isdiscontinued to prevent the follow-up downshift.
 9. The method accordingto claim 5, further comprising the steps of reducing the torque of thedrive motor relative to the torque derived from the driver's wish,during traction operation of the drivetrain to carry out the successiveupshifts; and increasing the torque of the drive motor relative to thetorque derived from the driver's wish, during each of the successiveupshifts carried out to carry out the successive upshifts during thrustoperation of the drivetrain.
 10. The method according to claim 6,further comprising the steps of reducing the torque of the drive motorrelative to the torque derived from the driver's wish, during tractionoperation of the drivetrain to carry out the successive upshifts; andincreasing the torque of the drive motor relative to the torque derivedfrom the driver's wish, during each of the successive upshifts carriedout to carry out the successive upshifts during thrust operation of thedrivetrain.
 11. The method according to claim 7, further comprising thesteps of reducing the torque of the drive motor relative to the torquederived from the driver's wish, during traction operation of thedrivetrain to carry out the successive upshifts; and increasing thetorque of the drive motor relative to the torque derived from thedriver's wish, during each of the successive upshifts carried out tocarry out the successive upshifts during thrust operation of thedrivetrain.
 12. The method according to claim 1, further comprising thestep of carrying out the first upshift or the first downshift uponreaching a synchronization point.